• 센서학회지
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• 제26권4호
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• pp.235-238
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• 2017

In this study, the design of a tri-axis micromachined gyroscope is proposed and the vibration characteristic of the structure is analyzed. Tri-axis vibratory gyroscopes that utilize Coriolis effect are the most commonly used micromachined inertial sensors because of their advantages, such as low cost, small packaging size, and low power consumption. The proposed design is a single structure with four proof masses, which are coupled to their adjacent ones. The coupling springs of the proof masses orthogonally transfer the driving vibrational motion. The resonant frequencies of the gyroscope are analyzed by finite element method (FEM) simulation. The suspension beam spring design of proof masses limits the resonance frequencies of four modes, viz., drive mode, pitch, roll and yaw sensing mode in the range of 110 Hz near 21 kHz, 21173 Hz, 21239 Hz, 21244 Hz, and 21280 Hz, respectively. The unwanted modes are separated from the drive and sense modes by more than 700 Hz. Thereafter the drive and the sense mode vibrations are calculated and simulated to confirm the driving feasibility and estimate the sensitivity of the gyroscope. The cross-axis sensitivities caused by driving motion are 1.5 deg/s for both x- and y-axis, and 0.2 deg/s for z-axis.

• 한국자기학회지
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• 제5권1호
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• pp.1-7
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• 1995

급속응고법중 단롤법을 이용하여 Fe-B계에 Co 및 Nb과 Al이 치환된 (Fe/sub 0.85/Co/sub 0.15/)/sub 75/ Al/sub 7/B/sub 18-x/Nb/sub x/(x = 2, 4, 6)와 (Fe/sub 0.85/Co/sub 0.15/)/sub 75/Al/sub y/B/sub 21-y/Nb/sub 4/ (y = 3, 5, 7, 9)합금을 급속응고장치로 단롤법을 이용하여 리본상으로 제작한후, 이들 합금의 초미세결정립 제조 가 능성과 자기적 특성의 조성 및 온도 의존성을 조사하였다. 초미세결정립합금은 y = 9를 제외한 전조성에서 제조가 가 능하였다. 포화자화 값은 열처리 후 증가하였고 Nb 함량이 증가하면 감소하였으며 상대적으로 Al과 B의 영향은 적었 다. 50 kHz에서 조사한 초투자율은 초미세결정립이 형성된 후가 열처리 전보다 2배이상 증가하였으며, 항자력과 교류 자기이력손실은 반대로 1/2이하로 감소하였다.

• 한국물환경학회지
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• 제22권6호
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• pp.1119-1122
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• 2006

Aeration by using diffusers usually requires approximately 50~90% of the total electricity needed to operate WWTP (WasteWater Treatment Plant)s. Accurate evaluation of the oxygen transfer efficiency for an aeration system, and recommendation of a better alternative may help saving WWTP operational costs. Appropriate techniques and methods to achieve this purpose have not been introduced in Korea. In this study, in-process analysis was performed for a coarse bubble aeration system by the off-gas method to evaluate its applicability in Korea. To accomplish this analysis, an off-gas test, unsteady-state clean water test and steady-state off-gas column test was conducted and comparisons to other aeration systems were made. The ${\alpha}$ and the F estimated from the results of the unsteady-state clean water test and the steady-state off-gas column test were 0.61 and 0.90 respectively in a coarse bubble aeration system. The comparison of P.E tube diffusers laid out single spiral roll and ceramic dome diffusers laid out full floor coverage showed that the oxygen transfer efficiency of the coarse bubble aeration system was less than or similar to other aeration systems. But, airflow rates per unit area were 4~5 times greater than other aeration systems. In regards to the oxygen transfer efficiency for airflow rates per unit area, a retrofit to higher efficiency diffusers was urgently needed. This study showed proved that off-gas methods can apply to evaluate diffuser performances to estimate operating factors and to compare other aeration systems in Korea.

• 한국재료학회지
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• 제3권2호
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• pp.175-184
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• 1993

Nd-Fe-B계에 Co와 Al을 첨가한 자석합금을 진공유도용해로에서 제조하여 이들 합금을 단롤법으로 melt-spun시켜 급냉리본을 얻었다. 제작된 급냉리본의 냉각속도에 따른 자기적 성질의 변화를 조사하였고, 최적의 급냉속도에서 제작된 리본을 파쇄하여 resin bond 자석을 제조하였으며, 이들 급냉리본 및 bond자석의 자기적 성질, 미세구조, 결정구조에 관하여 연구, 조사하였다. 이들 급냉리본의 자기적 성질은 급냉속도에 따라 크게 변하였으며 20m/sec전후에서 최적의 자기적 성질을 보였다. 이때의 급냉리본의 미세조직은 Nd-rich의 입계상이 미세한 N$d_2$F$e_14$B결정립을 둘러싼 cell 형의 구조였으며, 특히 Al이 2.1at%첨가된 리본시료에서는 iHc=15.5KOe, Br=7.8KG, (BH)max=8.5MGOe의 자기적 성질을 나타내었다. 최적의 급냉속도에서 제작된 리본을 polyamide resin과 2.5wt%의 비율로 혼합하여 상온에서 성형, 결합시켜 제작한 bond자석에서 보다 현저히 향상되었으며 유지시간이 8분인 경우 iHc=10.8KOe, Br=7.3KG, (BH)max=8.0MGOe의 값을 가졌다. 한편, 자구구조는 maze pattern이 주로 관찰되어 자화용이축인 C축이 배열되었으며 bond자석에서보다 hot-press 자석에서 자구폭이 보다 작았다.